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Chrysler 8.25 with 4.56 Yukons install

87xjco

NAXJA Forum User
Chris (Sting25) has a 1998 XJ with lot's of lift, 33" tires and 3.07 gears, he brought it to me to install 4.56 gears in his rear Chrysler 8 1/4 and the front HP30
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Chris purchased Yukon gears and master kits, the 8 1/4 does not require a new carrier, but the pinion cross shaft will need to be ground in order to clear the ring gear on re-install

First I remove the retaining bolt and slide out the cross shaft
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Then the axles can be pushed in and the C clips removed
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I'll use a center punch to mark the left cap with one mark and the right cap with 2. then i'll remove the carrier cap bolts, this also frees the side carrier adjuster nuts that are used to adjust carrier bearing position and preload

I will then knock out the races, there are two spots in the casting that allow a punch to contact more of the race surface when driving them out
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I'll install new races by using the old races, a long round punch and hammer as drivers, and tapping them in until they are seated in the housng
 
After the carrier is out I remove the pinion nut with a 1 1/4 socket, and then tap out the pinion gear, big difference between the old 3.07 pinion and the new 4.56 pinion
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I then need to remove the old inner carrier bearing so I can measure the shim that is between it and the back face of the pinion gear. My Yukon bearing remover makes quick work of removing the bearing
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I found this .025" shim was installed, there's no damage to the shim so I will just use it on the new pinion gear
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Then the new inner pinion bearing gets pressed on with the old shim in place
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Now the pinion gear can be installed in the housing and I will leave out the crush sleeve for now, I coat the bearings with some oil and use the old pinion nut and tighten it down until I feel some resistance when turning the pinion, roughly equal to what the final pinion bearing pre-load will be

Then I remove both carrier bearings
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And press on new bearings, if i'm carefull, I can press both bearings on at the same time, don't try this at home kids, if they get in a bind and cocked to the side, the problems it can cause are not worth the time savings
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I Coat those bearings with oil, install the ring gear with lock-tite on the bolts and tightened in a star pattern to 55ft lbs, now I am ready to install it in the housing

It's a little tricky to get the carrier, outer bearing cones, and side adjuster nuts all in place at the same time

My main concern is that I don't damage the threads on the adjuster nuts, I will first coat those threads with some anti-sieze. The housing on the right side has enough room that the adjuster nut can move outward and not need the threads engaged with the carrier cap before the cap is tightened, I can snug that cap down hand tight and then use my tool (more on the tool later) to spin the nut into the cap. But the left side nut must be set in with the threads partially engaged, so I take care that the threads are aligning properly so as I tighten down the left cap bolts, the nut turns freely, I found it is very easy to get the threads crossed and I had to keep backing off the cap and moving the nut slightly until the threads would align and I could easily rotate the nut when the cap bolts were snug.

This is a nice design, Once those nuts are in place it's very easy to adjust backlash and carrier bearing pre-load, no shim changes for the carrier are needed with this design
 
But i'm going to have to make a tool, those side adjuster nuts get tightened thru the axle tube, I need a long shaft that will turn the adjuster nuts

So I use a Toyota tortion bar and weld some plates on the end
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I make it fit inside the nut snug
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And I have a broken adapter that is 1/2 drive, i'll cut down the broken part
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And then weld it to the other end of the shaft
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I found one later on-line that sells for $59, and it's very similar to what I made

Spanner nut tool
http://completeoffroad.com/wsm/i-75_chrysler_spanner_tool_9_14_8_147_14.html
 
Now I tighten the side adjusting nuts until I have aprox. 008" backlash, and with the tool I made, I am able to torque the side nuts to 100ft lbs. for proper carrier bearing preload

Now i'm ready to run the pattern

Luckily on the first time, the drive side is good, the coast side is a little towards the inside of the teeth, but not bad, and I won't sacrifice the drive side position for the coast side. If the pattern were not good, I would have to remove the inner pinion bearing add or remove shims and press the bearing back on reinstall everything and run the pattern again, repeat until good.

Drive side
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Coast side
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So I remove the carrier and pinion gear, and now I am ready to install the crush sleeve, I will go ahead and install the pinion seal and new nut with lock-tite on the threads, then I tighten the nut until I feel resistance when turning, and then slowly tighten it a very small amount and I keep measuring the rotational force with my inch lb. torque wrench

I will go a few more inch pounds to allow for the extra drag from the pinion seal and pinion is all done
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Then I re-install the carrier and tighten the side adjuster nuts until I have backlash within the .006" to .010" spec

Here's the dial indicator zero'd out
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And here's the spec I ended up with .0075"
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The cap bolts were already torqued to 60ft lbs, the side nut retainer brackets are installed, I had to grind a groove in the cross shaft so it would clear the ring gear, then I used lock-tite on the cross shaft retainer bolt and installed it
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These gears are done

I move on and re-gear the front HP30, I won't do a whole write up now

But here's the patterns obtained
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Nice write! Thanks for taking the time!
 
Having the drive side pattern a little biased to the inside is not a bad thing on a offroad/performance application. It's a stronger pattern only problem is on a dd with stock tires you will hear more gear noise on accel..
 
nice write up... should have gone ahead and locked while you were in there... Also did you grind down the pin? I throught the best thing to do was save a little off a few teeth?
 
thats the case when you put a detroit in a 8.25 well at least all the ones we have done around here
 
sorry to revive an ancient thread, but - is there any hope of seeing the pictures that once went with this?
 
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